Electric filter



- April 16, G w PIERCE 1,997,599

ELECTRIC FILTER Filed July 19, 1952 I17 U6 71 for,

Gear 6 ll); Fierce I d-Homwy Patented Apr. 16, 1935 v g UNITED STATES PATENT OFFICE i 4 Q 4 l media stirrer. v I George Washington Pierce, Cambridge, Mass. Application July 19, 1932, Serial No. 623,357 Claims. (Gl.178-44) The present invention relates to vibratory syswith but a single stage of amplification. The terns and apparatus. and more particularly to transformer 20 may be connected to the source electrical systems and apparatus employing elecby means of the leads 2; and-the transformer l9 tromechanical vibrators, particularly magnetomay be connected to a suitable loador indicat 5 strictive devices. From a more limited aspect, ing device by means of the leads35 of the wind- 5 the inventionrrelates to magnetos'trictive filters. ing IS. The transformer 20, as hereinafter An object of the invention is to provide anew stated, may be an ordinary electromagnetic transand improved filter operating by magnetostricformen'or preferably may itself be a magnetotion. I v strictive transformer as is shown in the figure. 10 A further object is to provide anew and ime If it is desired to enhance the filter effect, the 10 proved magnetostrictive transformer. nd y be eenneeted, y means 01 e Another object is to provide-an electromagnetic leads 35, in the input circuit of a second amplishielding between two coils sothat electrical 'enfier 34, between the filament 36 and the grid ergy transferred from one coil to the other may 38. The magnetostrictive transformer l9 thus 5 be largely limited to the frequency of mechanical couples the output circuit of the first amplifier vibration. i j 4 with the input circuit of the second amplifier Other further objects will be explained here- 4- v A o l 4, Wi wh i P ti ed a ma inafter and will be particularly pointed out in netostrictive core 48, is connected in the output the appended claims. V circuit 'of thetube 34, between the filament 36 The invention will be explained in connection and the pla 0, 111 series with i p 20 with the accompanying drawing, the single figh C m y h p v d wi h a seeure of which is'a diagrammatic view of circuits ond winding 4B, and f m th r with and with and apparatus constructed and arranged accordthe winding 44 a magn'etostrictive transformer ing to a preferred embodiment of the present.in- 49- r The tr n rm r 49 may constitute the outvention, for filter purposes. e 7 put of the filter for connecting to the load, with 25 An amplifier tube 4, such as a vacuum tube two stages of amplification. I of the UY 227 type, is shown provided with an If a stillfurther enhanced filter'action is deinput circuit and an output circuit. The leads i h wi din 45 m y be disposed in he in- 2 are provided for connecting toa source of 91- P circuit third amplifier the Output ternating current of complex wave form from cir ui of wh h i 'P v .Wi h e primary 30 which a narrow-band. of frequencies is to be se- W di 54 O a t ansf rm r t Secondary lected and amplified. To this end,- the sour e winding of which, for connecting to the said load may be directly connected i i-the input circuit or indicating device is shown at 58. A plate batof the amplifier 4, between the filament Bend the tery 52 and a resistor 53, Say 01 0. 00 0, may be grid 8, but it is preferred, as illustrated, tolead connected in parallel with the winding 54, sep- 35 the energy fromthe 'source into the input circuit arated th r r y a condenser 1 of the amplifier 4 through the medium of an' in- S b e Stated; One mere 0! the pl yput transformer 20, theprimary winding 22 of inc -tubes may e m t d, in whic event the whichis connected with the source and th .resistor 53 and the condenser 55 will be disposed 40 ondary winding 24 of which is connected in the in the output circuit of th a amplifi r be 40 said input circuit. The input circuit may be e p y provided with a grid-biasing battery 25. The The inputand the output transformers shown output circuit of the amplifier 4, connected beat 20 and 56 of Fig. 1 may themselves be magnetotween the filament 6 and the plate l0, comprises strictive transformers of the type illustrated at a plate battery II and a. winding l4 within which H r 9, r they m y be of the ordinary f rm. 45 is axially positioned a magnetostrictive core Is, The drawing also shows certain effective meth- The core l6 may beof any form desired, as a rod ds of applyin r und connections to the appaor a tube, and may be'of any desired magnetoratus. Thus, the coils 22 and. 58 may beconstrictive material, as Monel metal. A second nected to a common ground 59, and the various winding l8, also positioned over the core l6, plate batteries, which may be acommon battery, forms with the winding l4 and-the core IS a are preferably grounded at 6|. Theshieldmagnetostrictive transformer 19. 1 The elements 8. h f mentioned, 'pl' el bly also thus far described constitute a magnetostrictive grounded. v

filter, the transformer "constituting the input Current of the various frequencies present in 56 of the filter and the transformer "the output, the source connected with-the leads 2, after amstriction. Where a second stage of amplification is employed, the resonant frequency will be further amplified by theamplifier 34, and the am-. plified current will flow into the winding 44. Assuming that the core 46' is similarly tuned to the same frequency, the amplitude of the desired frequency will be urther enhanced in relation to undesired frequencies and be magnetostrictively transmitted to the winding 48, and so forth. A very effective magnetostrictive filter is thus provided, that will yield, in the output winding 58 of the transformer 56, a sharply narrow range of frequency near the frequency of the cores l6 and.

The sensitiveness and effectiveness of theapparatus' maybe further improved by electrical tuning of the circuits, as by a condenser (not shown) shunted about one or more of the coils of the magnetostrictive transformers and proper- 1y adjusted.

There is the possibility, however, that energy of undesired frequencies may pass from the winding l4 to the winding l8, and from the winding 44 to the winding 48, otherwise than magnetostrictively, as by direct electromagnetic induction. To prevent this, each winding is electromagnetically'shielded from all the other windings by enclosing it in a metal tube or housing which, at the same time, may seal the winding. The metal tube for the winding i4 is illustrated at 60 and that for the winding l 8 at 62, the tubes 60 and 62 being disposedend to end and separated from each other by a metal wall 64, provided with an opening 66 for the magnetostrictive core IS. The windings 44 and 48 are similarly respectively enclosed in metal tubes 68 and 10, separated by a metal wall 12 provided with an opening I4 for the magnetostrictive core 46. The energytransferre'd between the windings l4 and I8, I

as between the windings 44 and 48, will thus be limited to that transferred by the magnetostrictive vibration of the cores l6 and 46.

- Preferably, the coils of the magnetostrictive transformers are positioned as near the center of the magnetostrictive core as possible. The coils are preferably so mounted as to allow on y sufficient clearance to permit free vibration of the core. The coils may each be about one-fourth the length of the core, and the thickness of the coils may be about one-seventh or one-eighth the length of the coil. The core, in the form of a rod, is mounted on a pin 16, which passes through an opening 18 in the central wall'64 or 12 and supports the magnetostrictive core so that it is mechanically free. However, slight friction caused by one end of the core accidentally touching the inside of the coil when mounted in this 'way is found to be without deleterious effect upon the operation. 7 Two permanent magnets 80 and 82 are mounted outside the shields to produce a sufiicient permanent field.

The magnetostrictive devices need not necessarily be of the form shown. The magnetostrictive vibrators may, for example, each be in the form' of a tube in which the associated winding is enclosed, as disclosed in a copending application, Serial No. 592,320,-filed February 11, 1931. Indeed, the tubes 60, 62, 68 and 10, if of suitable magnetostrictive material, may themselves be the magnetostrictive cores. As 'is further explained in the said application, one magnetostrictive winding I4, in the output circuit of the tube 4, may be placed inside of the vibrator housing 60, and the other winding 18 placed outside. The vibrator housing 60 will in this case also act as an electromagnetic shield, so that action of one of the windings on the other may be prevented to any desired extent, except at or near the frequency or frequencies which cause the vibrator housing 60 to vibrate. By suitably positioning one or both of the coils, which may be adjustably movable along the direction of their axes, the intensity and sharpness of frequency selection may be adjusted. This arrangement is an important element in a magnetostrictive filter structure.

It will be understood that the invention is not restricted to the illustrated embodiment thereof, but is susceptible to further modifications and change within the skill of the'artisan, and all such modifications and changes are considered to fall within the spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. An electric filter comprising an input circuit for connecting to a source of electromotive force, an output circuit, means for magnetostrictively coupling the circuits, and means preventing coupling of the circuits except by the said magnetostrictive means.

2. An electric ,filter comprising an input circuit having a winding for connecting to a source of electromotive'force, an output circuit'having a winding, a magnetostrictive core magnetostricr tively coupling the windings together, and means for shielding the windings.

3. An electric'filter comprising a vacuum tube having an input circuit and an output circuit, a second vacuum tube having an input circuit and an output circuit, means for magnetostrictively coupling the first-named output circuit and the second-named input circuit, and means for preventing coupling of the said first-named output circuit and the said second-named input circuit except by said magnetostrictive means.

4. An electric filter comprising avacuum tube having an input circuit and an output circuit having a winding, a second vacuum tube having an input circuit having a winding and an output circuit, a magnetostrictive core magnetostrictively coupling the windings together, and means for shielding the windings. I

5. An electric filter comprising a plurality of vacuum tubes each having an input circuit and an output circuit, and means magnetostrictively coupling selected output circuits of various tubes with selected input circuits of other tubes, the magnetostrictive means being operable at substantially the same frequency.

6. An electric filter comprising a plurality of vacuum tubes each having an input circuit and an output circuit, a plurality of the circuits each having a winding, andmagnetostrictive cores magnetostrictively coupling windings of selected output circuits of various tubes with windings of selected input circuits of other tubes, the cores being operable. at substantially thesame frequency. I

'7. An electric system comprising a space-current device having an input circuit and an output circuit, means for connecting with the input circuit a source of alternating current or voltage of a plurality of frequencies, a second space-current device having an input circuit and an output circuit, the input circuit of the second space-current devicebeing coupled tothe output circuit of the first-named space-current device, means for magnetostrictively transmitting selectively alternating-current quantities of predetermined frequencies to the input circuit of the second spacecurrent device, a third space-current devicelhaving an input circuit and an output circuit, the input circuit of the third space-current device being coupled to the output circuit of the second space-current device, and means for magnetostrictively suppressing from the input circuit of the third space-current device all alternatingcurrent residual quantities except those of the predetermined frequencies.

8. An electric system comprising a space-current device having an input circuit and an output circuit, magnetostrictive means for connecting with the space-current device a source of alternating voltage of a plurality of frequencies, and means for magnetostrictively suppressing from the circuit all alternating-current quantities of the source except those of predetermined frequencies.

9. An electric filter comprising a space-current device having an input circuit and an output circuit, means for magnetostrictively connecting the input circuit to a source of electromotive force, and means for magnetostrictively connecting the output circuit to a load.

10. A magnetostrictive transformer comprising two shielding housings, a winding in each housing, and a magnetostrictive core common to the windings, said core being designed for relatively free mechanical vibration by magnetostrictive action. V

11. A magnetostrictive transformer comprising a plurality of metallic tubular compartments, a winding in each compartment, and a magnetostrictive core common to the windings, said core being designed to vibrate mechanically with only such restraint as is essential for effective support.

12. A magnetostrictive transformer comprisingtwo shielding housings separated by a wall having. an opening, an energizing winding in each housing, and a magnetostrictive core for the windings disposed in the housings and extending through the opening.

13. A magnetostrictive transformer comprising two shielding housings separated by a wall having two openings, an energizing winding in each housing, a magnetostrictive core for the windings disposed in the housings and extending through one of the openings, and a pin for supporting the core disposed in the other opening.

14. A magnetostrictive transformer comprising two shielding housings, a winding in each housing, and a magnetostrictive core coupling the windings.

15. A magnetostrictive vibrator comprising a winding for alternating current and having a magnetostrictive field, a magnetostiictive core in the magnetostrictive field, and a shielding housing in which the winding and the core are disposed.

16. A magnetostrictive vibrator comprising a winding for alternating current, and means for sealing the winding and for magnetostrictively reacting upon the current in the winding.

17. A magnetostrictive device comprising a plurality of circuits, and means operating magnetostrictively to transfer electrical energy from one circuit to another solely at frequencies near a natural frequency of vibration of the. magnetostrictively operating means and to shield the circuits from each other.

GEORGE W. PIERCE. 

